/**************************************************
* File name: sm3_with_preprocess.c
* Author: HAN Wei
* Author's blog: https://blog.csdn.net/henter/
* Date: Nov 17th, 2018
* Description: implement SM3 hash calculation with 
    preprocess functions
**************************************************/

#include <string.h>
#include <openssl/evp.h>
#include "sm2_cipher_error_codes.h"
#include "sm3_with_preprocess.h"

/*********************************************************/
int sm3_digest_z(const unsigned char *id,
                 const int id_len,
		 const unsigned char *pub_key,
		 unsigned char *z_digest)
{
	int id_bit_len = id_len * 8;
	unsigned char entl[2];
	unsigned char sm2_param_a[32] = {0xff, 0xff, 0xff, 0xfe, 0xff, 0xff, 0xff, 0xff,
	                                 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
					 0xff, 0xff, 0xff, 0xff, 0x00, 0x00, 0x00, 0x00,
					 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xfc};
	unsigned char sm2_param_b[32] = {0x28, 0xe9, 0xfa, 0x9e, 0x9d, 0x9f, 0x5e, 0x34,
		                         0x4d, 0x5a, 0x9e, 0x4b, 0xcf, 0x65, 0x09, 0xa7,
					 0xf3, 0x97, 0x89, 0xf5, 0x15, 0xab, 0x8f, 0x92,
					 0xdd, 0xbc, 0xbd, 0x41, 0x4d, 0x94, 0x0e, 0x93};
	unsigned char sm2_param_x_G[32] = {0x32, 0xc4, 0xae, 0x2c, 0x1f, 0x19, 0x81, 0x19,
		                           0x5f, 0x99, 0x04, 0x46, 0x6a, 0x39, 0xc9, 0x94,
					   0x8f, 0xe3, 0x0b, 0xbf, 0xf2, 0x66, 0x0b, 0xe1,
					   0x71, 0x5a, 0x45, 0x89, 0x33, 0x4c, 0x74, 0xc7};
	unsigned char sm2_param_y_G[32] = {0xbc, 0x37, 0x36, 0xa2, 0xf4, 0xf6, 0x77, 0x9c,
		                           0x59, 0xbd, 0xce, 0xe3, 0x6b, 0x69, 0x21, 0x53,
					   0xd0, 0xa9, 0x87, 0x7c, 0xc6, 0x2a, 0x47, 0x40,
					   0x02, 0xdf, 0x32, 0xe5, 0x21, 0x39, 0xf0, 0xa0};
	unsigned char x_coordinate[32];
	unsigned char y_coordinate[32];
	EVP_MD_CTX *md_ctx;
        const EVP_MD *md;
	
	if ( !(id) || !(pub_key) || !(z_digest) )
	{
	   return INVALID_NULL_VALUE_INPUT;
	}

	if ( (id_bit_len <= 0) || (id_bit_len > 65535) )
	{
	   return INVALID_INPUT_LENGTH;
	}
	
	entl[0] = (id_bit_len & 0xff00) >> 8;
	entl[1] = id_bit_len & 0xff;
	memcpy(x_coordinate, (pub_key + 1), sizeof(x_coordinate));
	memcpy(y_coordinate, (pub_key + 1 + sizeof(x_coordinate)), sizeof(y_coordinate));
	
	md = EVP_sm3();
        if ( !(md_ctx = EVP_MD_CTX_new()) )
	{
#ifdef _DEBUG
           printf("Allocate a digest context failed at %s, line %d!\n", __FILE__, __LINE__);
#endif
	   return COMPUTE_SM3_DIGEST_FAIL;
	}
        EVP_DigestInit_ex(md_ctx, md, NULL);
        EVP_DigestUpdate(md_ctx, entl, sizeof(entl));
	EVP_DigestUpdate(md_ctx, id, id_len);
	EVP_DigestUpdate(md_ctx, sm2_param_a, sizeof(sm2_param_a));
	EVP_DigestUpdate(md_ctx, sm2_param_b, sizeof(sm2_param_b));
	EVP_DigestUpdate(md_ctx, sm2_param_x_G, sizeof(sm2_param_x_G));
	EVP_DigestUpdate(md_ctx, sm2_param_y_G, sizeof(sm2_param_y_G));
	EVP_DigestUpdate(md_ctx, x_coordinate, sizeof(x_coordinate));
	EVP_DigestUpdate(md_ctx, y_coordinate, sizeof(y_coordinate));
        EVP_DigestFinal_ex(md_ctx, z_digest, NULL);
        EVP_MD_CTX_free(md_ctx);
	return 0;
}

/*********************************************************/
int sm3_digest_with_preprocess(const unsigned char *message,
                               const int message_len,
                               const unsigned char *id,
			       const int id_len,
			       const unsigned char *pub_key,
                               unsigned char *digest)
{
	int error_code;
	unsigned char z_digest[32];
	EVP_MD_CTX *md_ctx;
        const EVP_MD *md;
	
	if ( error_code = sm3_digest_z(id,
	                               id_len,
				       pub_key,
				       z_digest) )
	{
#ifdef _DEBUG
           printf("Compute SM3 digest of leading data Z failed at %s, line %d!\n", __FILE__, __LINE__);
#endif
	   return COMPUTE_SM3_DIGEST_FAIL;	
	}

	md = EVP_sm3();
        if ( !(md_ctx = EVP_MD_CTX_new()) )
	{
#ifdef _DEBUG
           printf("Allocate a digest context failed at %s, line %d!\n", __FILE__, __LINE__);
#endif
	   return COMPUTE_SM3_DIGEST_FAIL;
	}
        EVP_DigestInit_ex(md_ctx, md, NULL);
        EVP_DigestUpdate(md_ctx, z_digest, sizeof(z_digest));
	EVP_DigestUpdate(md_ctx, message, message_len);
        EVP_DigestFinal_ex(md_ctx, digest, NULL);
        EVP_MD_CTX_free(md_ctx);
	return 0;
}